This invention is directed to a mold and die casting apparatus including a compact core position sensor unit.
In mold and die casting systems, one or more core members of a mold body must be accurately positioned between opened and closed positions. A typical application is disclosed in copending application entitled "Threaded Actuator For Positioning Structure Subject To Intense Load" filed on Dec. 15, 1998 with Ser. No. 09/211,536 and assigned to the assignee of this application. In such application, a movable core is mounted to a core slide within a core cavity and coupled to a threaded actuator secured to the mold base or the like. The threaded actuator includes a hydraulic cylinder unit having a piston and piston rod connected to the core slide. The cylinder unit is specially constructed to establish a high locking force system between the piston rod and the cylinder thereof such that with the core appropriately located, the core is held in place under a very intense force, often greater than the cylinder motor force. In this and like applications, the accuracy of the core positioning is dependent on the accurate detection of the sensing and location of a locking member connected to the piston rod of the hydraulic cylinder unit or other prime mover. In a particularly practical and efficient system presently manufactured and sold, sensing units are connected to the hydraulic cylinder unit to detect the fully extended loaded position as well as the fully retracted position, and thereby the limits of the core slide and core. The sensing unit is attached to, and projects outwardly, from the cylinder unit. Because of various mounting systems for the hydraulic cylinder in relation to the associated equipment of the mold system, the size of the sensors must fall within certain restrictions to avoid interference with the adjoining structures. The present structure provided by the assignee uses a very small Hall effect cell based sensor which has a length of slightly less than one inch and threads into the cylinder block, with the sensing end located in accurate spaced position for detection of the loaded and the retracted positions of the actuator unit. One sensor is secured to the side of a cylinder unit to detect the forward or load position of the actuator. A second sensor is connected to the outer end of the cylinder unit to detect the retracted or release position of the actuator. One present sensor unit which has produced highly successful location detection is a integrated circuit switch using a NPN Hall effect position sensing system. The system requires a power source connection providing an output to a computer system processing the sensed signal which interconnects the output to actuate a suitable relay system. This is a relatively expensive system and employs a somewhat fragile construction and which must be adapted to each particular available voltage system. A computer interface is necessary to provide a universal connection to any type of a control system without the necessity of special conversion systems or circuitry. Although it is found to provide an exceptionally satisfactory system, the unit adds significantly to the total cost and complexity of the apparatus.
A simple sensing relay switch is preferred as it functions as a simple on/off switch and eliminates interface circuitry and expense. However, such alternative available switches providing a simple on/off switching contact have been costly and significantly only been constructed with interfering lengths, generally a minimum of three inches in length. Although the relay type switch should provide a less expensive system, the system has not in fact been less costly because of the switch cost and has not been readily accepted in many applications because of physical interference between the switch and various associated components of the mold and die casting system. Further, the available switch does not include an accurate depth setting method. The relatively large extension of the switch is also prone to damage thereof.